diff -r c5318497a0b6 -r f05aeee71a14 src/EditProductTab8.cpp
--- a/src/EditProductTab8.cpp	Mon Jul 11 17:03:55 2022 +0200
+++ b/src/EditProductTab8.cpp	Tue Jul 12 12:10:20 2022 +0200
@@ -484,6 +484,10 @@
     Acid = round(Acid * 100.0) / 100.0;
     product->sparge_acid_amount = Acid / 1000;
     ui->sp_acidvolEdit->setValue(Acid);
+
+    product->est_preboil_ph = -log10(((pow(10, -product->mash_ph) * product->wg_amount) + (pow(10, -product->sparge_ph) * product->brew_sparge_est)) / (product->wg_amount + product->brew_sparge_est));
+    ui->preboil_phEdit->setValue(product->est_preboil_ph);
+    ui->brew_preboilphShow->setValue(product->est_preboil_ph);
 }